So what are the "BEST Practices" for making People and Cars to animate?

Have cars and people to walk and move out of view never to return to the seen of the crime? Set a clip to just animate that 10 second clip before moving on and out of view? My project flyby movies typically fly around the building or see the same areas more than once so I see the same person reset back to the start position which is odd to view in the movie.